Don't care when you get married? Think off-season.
Depending upon where you live, there are generally a few months when it seems like no one is getting married. For those in the northern half of the country, that is usually during late winter and early spring (January-March), when the weather is often dreary and unpredictable. For those in the southern half, many brides avoid planning their wedding during the heat and humidity of summer (July-September).
If you truly don't care about the weather, you should consider planning during these months. Although, if a large percentage is coming from out of town, this may not be the best idea (the last thing you want is your mother's family passing out from heat stroke in Phoenix). However, if your guests are from the same region, this is an excellent way to help ensure that you will get a better selection of venues and vendors available (some even offer discounts for off-season weddings). Popular wedding months are also difficult for guests, who sometimes have to choose between what weddings to attend. Giving them an invitation during these months will probably increase your chances that they can attend.